side vents for and aft on hull

[Blue_Heron]

Ok, so the question is; why have bilge vents on an outboard boat?

As Denny (Bushwacker) and Jim (77SceptreOB) mentioned early in the thread, bilge vents allow air to circulate in the bilge to keep moisture levels down. A sealed bilge with even a small amount of water in it is going to create a mini diurnal water cycle. During the day, the hull will heat up and water in the bilge will evaporate. At night, when the hull cools down, the humidity will condense on the inner surface of the hull and the underside of the deck. Polyester based fiberglass is not waterproof. Constant or frequent exposure to liquid water is going to cause it to soak up moisture I can't see that being good for the wood core in the decks and transoms of these boats.

In a vented bilge, humid air will be replaced with outside air. The air in the bilge is more likely to be close in temperature to the hull, which should reduce condensation in the bilge. The safety concern over fuel spilled in the bilge has already been discussed. To me it's a lesser issue in an outboard boat. All electrical equipment in your bilge should be labeled "ignition protected" anyway.

To me, the reasons for having the vents outweigh the aesthetic considerations. Personally, I like the look. It says "function" in a world where we've sometimes lost track of the reasons we do things.

Dave